Admob

Steps to do before:

Identify your publisher ID on the top right of your dashboard, starts with pub-xxxxxxxxxx.

Open the Monetize tab and create an ad unit for your application. You should be able to see your ad unit after selecting an app on your left panel.

An Ad Unit ID is a unique identifier given to the places in your application where ads are displayed. If you had an app with two activites, for example, each displaying a banner, you’d have two ad units, each with its own ID. Your Ad Unit ID starts with ca-app-pub-xxxxxxxxxxxxxx/xxxxxxx

Download the Google Play Services Library using the Android SDK Manager.